Place celery in a medium saucepan; cover with salted water, and lay celery leaves on top. Bring to a boil; cook 10 minutes or until tender. Discard leaves, and drain celery, reserving 3/4 cup liquid; set aside.
Melt 3 tablespoons butter in a heavy saucepan over low heat. Add flour; cook 1 minute, stirring constantly, until mixture is smooth. Gradually add half-and- half and celery liquid; cook over medium heat, stirring constantly, until sauce is thickened and bubbly.
Place a layer of celery in a lightly greased 2 1/2-quart casserole. Spoon half the sauce over celery; sprinkle with half the almonds. Repeat layers. Top with breadcrumbs, sprinkle with cheese, and dot with remaining butter. Bake at 350° for 30 minutes.